Reference found where even-sized list expected

Win has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

Why does this line:


  my (%hashref_return_A) = correlation(\@primarys_array, \@secondarys_
+array);
[download]

give me this warning:


Reference found where even-sized list expected at script.pl line 576
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The subroutine is taking the request like:


sub correlation {


  my ($x_ref, $y_ref) = @_;   
  

  my $lfit = Statistics::LineFit->new();
  $lfit->setData($x_ref, $y_ref);
[download]

Comment on Reference found where even-sized list expected Select or Download Code

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Re: Reference found where even-sized list expected by moritz (Cardinal) on Nov 29, 2007 at 12:03 UTC
It looks like the sub returns a hash ref, and you try to store it in a hash. There are two ways around it `# 1) store it in a reference: my $hashref = correlation(\@primarys_array, @secondarys_array); # 2) deference it and store it in a hash: my %hash = %{ correlation(\@primarys_array, @secondarys_array) };` [download] I recommend the first one, though. See perlreftut for more details.	[reply] [d/l]
Re: Reference found where even-sized list expected by jhourcle (Prior) on Nov 29, 2007 at 12:08 UTC
What is returned from correlation (or the last statement in correlation, if you don't specifically return a value? From the error given, I'm going to assume it's a reference of some form ... however, when declaring a hash in the way that you have, you need to specify a list of pairs (ie, an even sized list), rather than a reference. Just for debugging, you might want to examine what's being returned from correlation: `my @return = correlation(\@primarys_array, \@secondarys_array); use Data::Dumper; warn Dumper \@return;` [download] As you've named the variable 'hashref_return_A', I'm going to assume the return is a hashref, and not a hash. In which case, you'll want to use one of the following: `# note -- it's a scalar ($) not a hash (%) my $hashref_return_A = correlation(\@primarys_array, \@secondarys_arr +ay); # or # %{ ... } casts a hashref to a list my (%hashref_return_A) = %{ correlation(\@primarys_array, \@secondarys +_array) };` [download]	[reply] [d/l] [select]